Device for removing undesirable frequencies from electric circuits



March 30, 1937. MIYAZAK, 2,075,218

DEVICE F OR REMOVING UNDESIRABLE FREQUENCIES FROM ELECTRIC CIRCUITSFiled July 3, 1935 'INVENTOR;

Patented Mar. 30, 1937 UNITED STATES DEVICE FOR REMOVING UNDESIRABLEFREQUENCIES FROM ELECTRIC CIR- CUITS Jisuke Miyazaki, Tokyo, JapanApplication .r'uiya, 1935, Serial No. 29,758

2 Claims.

My invention relates to improvements in a device for removing theundesirable frequencies from a-communication line and has for itsprincipal object to provide a device whereby the dis- 5 turbance causedby the voltage induced electromagnetically in the communication line maybe removed in a simple and positive manner.

According to my invention, the voltage similar to that inducedelectro-magnetically in the communication line from the adjacent powerline is produced and the voltage is amplified through an electric valveamplifier and stepped down by a transformer and is supplied to thecommunication line to be protected in an opposite'phase to that of theinduced voltage.

For a more complete understanding of my invention referenceshould now behad to the drawing in which:

Fig. 1 is a diagram illustrating an embodiment of my invention and,

Fig. 2 illustrates another modification of my invention. e

In these figures, the same reference characters designate similar parts.

Referring more particularly to Fig. 1l9 designates a communication lineto be protected. A protecting wire V2!) is stretched along thecommunication line I9. The wire 20 is grounded at more than two points.A voltage of the same wave form as that of the induced Voltage on thecommunication line will be induced on the wire 20 by the electromagneticinduction from the adjacent power lines. The protecting wire 20 includesa primary winding 5 of a transformer 4 and its secondary winding 6isconnected to the grid of an amplifier valve 1. The plate circuit ofthe amplifier valve 1 includes the primary winding 9 of a transformer 8.The secondary windings Ill and ID of the transformer 8 are inserted inthe respective line of the communication line IS in such a. manner thatthe induced voltage on the line H! may be opposed by the inducedelectro-motive force of the winding I0. I l designates the B-battery ofthe amplifier valve I.

The operation of the arrangement is as follows: As above mentioned, thewave form of the induced voltage on the wire 20 is the same as that ofthe induced voltage on the communication line IS. The voltage having thesame wave 5 form as that of the induced voltage on the communicationline is thus produced and is stepped up through the transformer 4 andmagnified by means of the amplifier I. Since the magnified currentpasses through the primary-winding 9 of the transformer 8, its secondarywinding ill or III will induce a voltage exactly similar in wave form tothe induced voltage on the communication line IS. The secondary'inducedvoltage may be adjusted to be the same in magnitude but oppositein phase with that of the induced voltage on the communication line [9by suitably selecting the transformation ratio as well .as the polarityof the secondary windings l0 and ID with which the transformer 8 isconnected to the communication line I 9. Being magnified through theamplifier I, the terminal voltage across the primary winding 9 of thetransformer 8 will be very much increased comparing with the inputvoltage of the transformer 4. Accordingly, for obtaining a neutralizingvoltage of the same magnitude as that induced on the line I9, thetransformation ratio of the transformer 8 may be selected very largecomparing with that of the transformer 4. The number of turns of thesecondary winding Ill may thus be. selected to a small number asdesired. The distortion of speech due to the reflection at the coil isnot observed according to my invention.

Fig. 5 illustrates another modification of Fig. 4 in which'anothercommunication line'2l running in parallel to the communication line i9is used as the protecting wire of the latter. In this instance, thecommunication line-2| has drainage coils,at least, at two points and theinput transformer 4 has two primary windings 5 and 5' which. areinserted in the respective line of the telephone circuit 2|.

In, all of these embodiments of my invention any of the coupling devicesknown to the art may be adopted in supplying grid potential to theamplifier valve. While I have shown a particular embodiment of myinvention, it will be understood, of course, that I do not wish to belimited thereto since many modifications may be made, and I, there'-fore, contemplate-by the appended claims to cover any such modificationsas fall within the true spirit and scope of my invention. 1

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A device for removing the undesirable frequencies from acommunication line, comprising a communication line, a protecting wirestretched along said communication line and grounded at least at twopoints to induce a voltage having the same wave form as that of inducedvoltage on the communication line due to the electro-magnetic inductionfrom the adjacent power lines, an elec- 'tric valve amplifier, acoupling means for applying the induced voltage on said .protecting wire2 I v i tothe grid of said valve, and a transformer for transformingsaid magnified induced voltage to be same in magnitude while opposite inphase' with that of the induced voltage on said communication line, thesecondary winding of said transformer being inserted in saidcommunication line. v

2. A device for removing the undesirable frequencies from acommunication line, comprising electromagnetic induction from theadjacent power lines to said amplifier-valve, said communication circuitbeing grounded, at least, at

'two points through drainage coils, and an output transformer fortransforming said induced voltage magnified through said amplifier valveto be same in magnitude while opposite in phase with .that of theinduced voltage on the other communication circuit through thesame'e1ectromagnetic induction, the secondary winding of said outputtransformer being inserted in'said other communication circuit.

JISUKE MIYAZAKI. I

